Answer: Shelf
Step-by-step explanation:
I could not find the further explanation of your question but I have found on the internet that the correct answer is ''shelf''.
I assume that in your question should be the 'case' description but since i could not find it I will try to tell you something useful.
If we are talking about item number, we are considering a number that is identifying the item. Each item should have it. If you are looking for some item, you can put an item number into the search box to find it fastly.